import java.math.BigInteger;
import java.util.Scanner;

public class LQB_09 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        while(1 == 1) {
            long n = input.nextLong();// 排列组合 C(n,r)
            long number = 1, r = n / 2;
            for (int j = 1; j <= r; j++) {
                number = (number * n) / j;
                n--;
            }
            System.out.println(number);
        }
    }
}
